This invention relates generally to fire protection systems and, more particularly, to fire protection systems in which a plurality of individual fire suppressor units are simultaneously activated to extinguish a fire.
Certain fire protection systems employ a plurality of strategically located suppressor units, each including an extinguishant filled vessel and an electrically operated release mechanism for inducing discharge of the extinguishant in response to detection of a fire. When simultaneous operation of all suppressor units is desired, the system is provided typically with a control circuit that produces coincident activation of all release mechanisms. In such systems, it is common technique to electrically supervise the electric integrity of the release mechanisms by providing and monitoring a trickle current through a series connection thereof. Although this series supervision establishes a constant knowledge of release mechanism integrity, there remains the possibility that a single release member failure will cause failure of the entire series system. In addition, even a detected failure of a release mechanism can prevent system operation if the detected failure occurs coincidentally with a demand for system actuation.
A solution to this problem is provided in U.S. patent application Ser. No. 500,864, filed Aug. 27, 1974 now U.S. Pat. No. 3,917,001. The system disclosed in that application includes a circuit for switching the release mechanisms from a series to a parallel arrangement a short period after system activation is initiated. Although a substantial improvement over the prior art, the disclosed system requires a pair of electrical contacts for all but one of the individual release mechanisms employed and can require a plurality of relay windings in systems having a large number of release mechanisms.
The object of this invention, therefore, is to provide a reliable, less costly fire protection system of the type employing a plurality of individual suppressant units all having electrically operated release mechanisms adapted for coincident activation.